5.2 Natural selection

Question 1

What does natural selection depend on within populations?

Answer 1

Variation amongst members of the same species

Question 2

What is variation?

Answer 2

The presence of variety - the differences between individuals

Question 3

What are the 4 types of variations?

Answer 3

• Genetic
• Continuous
• Discontinuous
• Environmental

Question 4

What are the 3 causes of genetic variation?

Answer 4

• Mutations
• Meiosis
• Sexual reproduction

Question 5

How does mutations cause genetic variation?

Answer 5

Changes to the DNA sequence by gene mutations lead to new alleles, enlarging the gene pool of the population

Question 6

How does meiosis cause genetic variation?

Answer 6

Independent assortment and crossing over
* New combinations of alleles by breaking up the existing combination in a diploid cell

Question 7

How does sexual reproduction cause genetic variation?

Answer 7

Random fusion of gametes from two unrelated individuals
* Allows mutation that occured in different individuals to be brought together

Question 8

What are adaptations?

Answer 8

Characteristics that make an individual suited to its environment and way of life

Question 9

What are structural, behavioural and physiological adaptations?

Answer 9

Structural: Physical differences in biological structure
Behavioural: Differences in patterns of activity
Physiological: Differences in detection and response to surrounding

Question 10

Why is it important not to imply purpose to adaptaions?

Answer 10

According to evolutionary theory adaptations develop by natural selection, not with the direct purpose of making an individual suited to its environment.

Question 11

What is the Malthusian Dilemma?

Answer 11

• Population size increeases exponentially
• Resources only increase linearly
• More species produce more offspring than the environment can sustainably support
• This leads to competition within a population, causing the population growth to slow

Question 12

What are the consequences of species producing more offspring than the environment can support?

Answer 12

• Struggle for survival
• Competition for resources
• Not every individual will obtain enough to allow them to survive and reproduce

Question 13

Which type of individuals are more likely to survive and produce more offsrping when resources are competitive?

Answer 13

Individuals that are better adapted and they pass on the characteristics to their offsrping

Question 14

How does natrual selection allow for evolution?

Answer 14

Natural selection increases the frequency of characteristics that make individuals better adapted and decreases the frequency of other characteristics leading to changes within the speces - evolution by natural selection

Question 15

What are some selection pressures dependent on the population size?

Answer 15

• Predators
• Availability of resources (e.g. shelter, water)
• Nutrient supply (i.e. food source)
• Disease/pathogenic spread
• Accumulation of wastes

Question 16

What are some selection pressures that are not affected by the population size?

Answer 16

• Phenomena (e.g. natural disasters)
• Abiotic factors (e.g. temperature, CO2 levels)
• Weather conditions (e.g. floods, storms, etc)

Question 17

What is the galapagos finches an example of? (adaptive or convergent and why)

Answer 17

Adaptive radiation
* Darwin hypothesised that ‘fromm an original paucity of birds in this archipelago, one species had been taken and modified for their different ends’

Question 18

What is heritability?

Answer 18

The portion of the variation due to genes is called heritability

Question 19

How long after an antibiotic is introduced do the bacteria show resistance?

Answer 19

Within a few years

Question 20

Does resistance to antibiotic spread?

Answer 20

Yes, resistance to the antibiotic spreads to more and more species of pathogenic bacteria
* in each species the proportio of infections that are caused by a resistant strain increases

Question 21

How is evolution present in the resistance of antibiotics?

Answer 21

• During the time over which antibiotics have been used to treat bacterial diseases there have been cumulative changes in the antibiotic resistance properties of populations of bacteria.
• The development of antibiotic resistance is therefore an example of evolution

Question 22

What is antibiotic resistance due to?

Answer 22

Genes in bacteria and so it can be inherited

Question 23

What are 4 causes of the rapid evolution of multiple antibiotic resistance?

Answer 23

• Widespread use of antibiotics, both for treating diseases and in animal feeds used on farms
• Bacteria can reproduce very rapidly, with generation time of less than an hour
• Populations of bacteria are often huge, increasing the chance of a gene for antibiotic resistance being formed by mutation
• Bacteria can pass genes on to other bacteria in several ways, including using plasmids, which allow one species of bacteria to gain antibiotic resistance genes from another species